苏北平原河网区典型农村中小河流水体氮磷赋存特征

以苏北平原河网区的盐城市射阳县某个典型圩区(面积12.73km2)为例,通过连续15个月对圩区内沟渠河流水体采样分析,研究苏北平原河网区中小河流地表水氮磷赋存特征。结果表明:研究区域中小河流水体氮磷超标严重,水体处于富营养化状态。所有水样品总氮质量浓度均超过GB 3838—2002《地表水Ⅲ类水质标准》(ρ=1.0 mg/L),79%的总氮质量浓度超过Ⅴ类水质标准(ρ=2.0 mg/L);73%的总磷质量浓度超过Ⅲ类水体标准(ρ=0.2 mg/L),39%的样品超过Ⅴ类水质标准。地表水氮素和磷素主要以溶解态形式存在;硝态氮是溶解态总氮主要赋存形态,相应的比例约为60%,铵态氮比例最少,约为10%;溶解态活性磷是溶解态磷素主要赋存形态,约为80%。畜禽养殖相对集中区域地表水氮素和磷素浓度高于其他区域;中沟、干渠等小型河流水体在夏季存在水质分层现象。

Characteristics of nitrogen and phosphorus status of surface water in rural medium and small rivers in a plain river network region of North Jiangsu Province

Nitrogen and phosphorus status of surface water in rural medium and small rivers in a plain fiver network region of North Jiangsu Province were investigated. A case study was conducted in a typical polder area with an area of 12. 73 km^2 located in Sheyang County, in Yancheng City, through a continuous 15 months of sampling in rivers and ditches of the study area. The results show that the nitrogen and phosphorus contents in surface water of the study area significantly exceeded the national standard, and the surface water was in severe eutrophication status. Total nitrogen （TN） concentrations of the surface water samples were all beyond TN Category Ⅲ （ρ = 1.0 rag/L） of the National Water Quality Standard （ GB 3838-2002 ）. 79% of the water samples exceeded the Category Ⅴ standard （ρ = 2.0 mg/L） in TN concentration. Seventy-three percent of the water samples exceeded the Category Ⅲ standard （ρ = 0. 2 mg/L） in total phosphorus （TP） concentration, and 39% of the water samples exceeded the Category V standard （ρ =0. 4rag/L） in TP concentration. TN and TP in the surface water samples mainly appeared in the dissolved form. Nitrate-N was the main type of the dissolved form, and ammonium-N appeared in the dissolved form in the lowest proportion. The proportions of nitrate-N and ammonium-N in the dissolved nitrogen were 60% and 10%, respectively. Dissolved reactive phosphorus, with a proportion of 80%, was the main form of dissolved phosphorus. The nutrient contents of surface water in densely-located livestock and poultry breeding areas were higher than those in other areas. There existed water-quality stratification in small rivers in summer.